Unprotected Sex After The Period

Unprotected sex after the period : that means foruth day it will cause pregnancy One of my friend did unprotected sex with a girl after the period that means fourth day of the period. It will cause pregnancy or not. Because he given epl-72 pill for that girl with in 12hours. but she got two or three drops of bleeding after 4 days. her previews period on 18th feb. next period comes normally on that 18th march or it will take time. but she told to him date was come only on 18th march. its possible or he want to give pills to her period... Plz provide me as sooon as possible...